JP2801165B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having excellent output characteristics and overwrite characteristics and excellent running durability.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media have been widely used in the form of tapes, disks, drums or sheets. Such a magnetic recording medium is usually manufactured by applying a magnetic paint containing a magnetic powder and a binder as main components on a support. In recent years, in particular, there has been a demand for a magnetic recording medium to have a smaller size and a higher recording density. In order to respond to such a request, for example, it has been proposed to improve the coercive force Hc and the residual magnetic flux density Br of the magnetic layer and to reduce the thickness of the magnetic layer. The second between the magnetic layer and the support.
A so-called double coating method has been proposed in which a second layer and a magnetic layer are formed by multi-layer coating. However, the above proposal has a problem that the overwrite characteristics are deteriorated. Further, in the above proposal, it is necessary to make the flow characteristics of the coating material forming the magnetic layer and the coating material forming the second layer uniform, but they are not yet sufficiently uniform, and the magnetic layer and the coating material are not sufficiently aligned. However, there is a problem that the interface with the second layer is disturbed, the surface smoothness of the layer is impaired, and the electromagnetic conversion characteristics are reduced.

[0003] On the other hand, in a magnetic recording medium, the surface smoothness may be reduced due to poor dispersibility of the magnetic powder due to an excessive or insufficient content ratio of the binder to the magnetic powder. Further, when the amount of the binder is insufficient, the adhesive strength is reduced, and when the amount of the binder is excessive, a sticking phenomenon, a blocking phenomenon, and the like occur. Then, there is a problem that the running durability of the magnetic recording medium is reduced due to these causes.

For this reason, in order to improve both the overwrite characteristics and the running durability, for example, in US Pat. No. 5,178,935, the second layer is provided, and the second layer is provided. Include a magnetic powder and a binder, and a magnetic recording medium in which a vinyl chloride resin and / or a cellulose resin is used as the binder in an amount of about 3 to 24 parts by weight based on 100 parts by weight of the magnetic powder. However, even in the above proposal, the overwrite characteristics and the running durability of the magnetic recording medium are not yet sufficiently compatible, and the development of a magnetic recording medium excellent in both the overwriting characteristics and the running durability has been demanded. That is the current situation.

Accordingly, it is an object of the present invention to provide a magnetic recording medium which has good surface smoothness, and which is excellent in output characteristics, overwrite characteristics, and running durability.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the magnetic recording medium has a binder containing magnetic powder and a specific resin in the uppermost layer and a layer adjacent to the uppermost layer, respectively. And that the content of the binder and the specific resin between the two layers has a specific relationship, thereby achieving the above object.

The present invention has been made based on the above findings, and has a support and a plurality of magnetic layers provided on the support, and the plurality of magnetic layers are provided as an uppermost layer. in the magnetic recording medium comprising a first magnetic layer, a second magnetic layer provided adjacent to the magnetic layer of the first, second of the 1
The magnetic layer contains a binder containing a magnetic powder and a vinyl resin and / or cellulose resin chloride, the second the
The magnetic layer of the ferromagnetic powder and vinyl chloride resin and / or
A binder containing a cellulosic resin, wherein the content of the binder in the first magnetic layer and the content of the binder in the second magnetic layer have a relationship represented by the following formula, and A magnetic recording medium characterized in that the content of the vinyl chloride resin and / or the cellulose resin and the content of the vinyl chloride resin and / or the cellulose resin in the second magnetic layer have the following formula: To provide. 0.6 ≦ (AB) / B ≦ 6 0.4 ≦ (CD) / D ≦ 11 [where A is the content of the binder in the second magnetic layer /
Content of Magnetic Powder in Second Magnetic Layer>
<Content of binder in first magnetic layer / content of magnetic powder in first magnetic layer> indicates C, ((vinyl chloride resin and / or cellulose resin in second magnetic layer) Content of resin) / content of magnetic powder in second magnetic layer>.
D indicates <(content of vinyl chloride resin and / or cellulose resin in first magnetic layer) / content of magnetic powder in first magnetic layer>. ]

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described below in detail. First, a preferred configuration of the magnetic recording medium of the present invention will be described with reference to FIG.

A magnetic recording medium 1 of the present invention shown in FIG. 1 has a support 2 and a plurality of magnetic layers 3 provided on the support 2, and the plurality of magnetic layers 3 And a second magnetic layer 3b provided adjacent to the first magnetic layer 3a. A back coat layer 4 is provided on the back surface of the support 2 as necessary.

In the magnetic recording medium of the present invention, in addition to the support, the first magnetic layer, the second magnetic layer and the back coat layer, a support and a second magnetic layer or Other layers such as a primer layer provided between the back coat layer and a third magnetic layer provided for recording a servo signal or the like corresponding to a hard system using a long wavelength signal may be provided. .

As the support 2 used in the magnetic recording medium of the present invention, any of a magnetic support and a non-magnetic support can be used, but a non-magnetic support is particularly preferably used. As the non-magnetic support,
Generally known materials can be used without any particular limitation, but specifically, flexible films or disks made of a polymer resin; non-magnetic metals such as Cu, Al, Zn, etc., glass, porcelain, and ceramics Films made of ceramics, etc., etc.
Disks, cards, and the like can be used.

Examples of the polymer resin forming the flexible film or the disk include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate, and polyethylene bisphenoxycarboxylate; , Polyolefins such as polypropylene, cellulose acetate butyrate,
Cellulose derivatives such as cellulose acetate propionate, polyvinyl chloride, vinyl resins such as polyvinylidene chloride, or polyamide, polyimide, polycarbonate, polysulfone, polyetheretherketone, polyurethane, etc. Two or more can be used in combination.

In the magnetic recording medium of the present invention, the back coat layer provided on the back surface of the support as required can be formed by using a known back coat paint without any particular limitation.

In the magnetic recording medium of the present invention, the first magnetic layer provided on the support is an uppermost layer of the magnetic recording medium, that is, a layer provided as a layer located on the surface of the magnetic recording medium. The first magnetic layer is a layer containing a magnetic powder and a binder containing a vinyl chloride resin or a cellulose resin, and a first magnetic paint is applied on a second magnetic layer described later. It is formed by this. As the first magnetic paint, a paint mainly containing a magnetic powder, a binder containing a vinyl chloride resin or a cellulose resin, and a solvent is preferably used.

Examples of the magnetic powder used in the first magnetic paint include a ferromagnetic metal powder mainly composed of iron and a hexagonal ferrite powder. The coercive force of the ferromagnetic metal powder is preferably 1400 to 2500 Oe. The hexagonal ferrite powder has a coercive force of 9
It is preferably from 00 to 2300 Oe. When the coercive force of the ferromagnetic metal powder and the hexagonal ferrite are respectively less than the above lower limits, the short-wavelength RF output is reduced because of easy demagnetization. Is insufficient, the writing ability is insufficient, and the overwrite characteristics are further deteriorated.

The saturation magnetization of the ferromagnetic metal powder is
Preferably, it is 100 to 180 emu / g.
More preferably, it is 60 emu / g. The saturation magnetization of the hexagonal ferrite powder is preferably 30 to 70 emu / g, and more preferably 45 to 70 emu / g. When the saturation magnetization of the ferromagnetic metal powder and the hexagonal ferrite powder are each less than the lower limit, the filling rate of the magnetic powder is reduced, the output is reduced, and when the upper limit is exceeded. Therefore, it is necessary to reduce the binder, the interaction between the magnetic powders increases, and as a result, the magnetic powders are in an agglomerated state, and it is difficult to obtain a desired output. Is preferred.

Therefore, the coercive force of the first magnetic layer containing the ferromagnetic metal powder is preferably from 1500 to 2400.
Oe, more preferably 1600 to 2200 Oe,
The coercive force of the first magnetic layer containing the hexagonal ferrite powder is preferably 1100 to 2200 Oe.
The first magnetic layer containing the ferromagnetic metal powder preferably has a saturation magnetic flux density of 3000 to 4500 gauss,
More preferably, it is 3200 to 4000 Gauss, and the saturation magnetic flux density of the first magnetic layer containing the hexagonal ferrite powder is preferably 1500 to 2500 Gauss, more preferably 1600 to 2300 Gauss.

The ferromagnetic metal powder has a metal content of 5%.
0% by weight or more, and 60% by weight or more of the metal component is Fe.
Ferromagnetic metal powder. Specific examples of the ferromagnetic metal powder include, for example, Fe-Co, Fe-Ni,
Fe-Al, Fe-Ni-Al, Fe-Co-Ni, F
e-Ni-Al-Zn, Fe-Al-Si, and the like. The shape of the ferromagnetic metal powder is needle-like or spindle-like, and its major axis is preferably 0.05 to 0.25 μm,
More preferably, it is 0.05 to 0.2 μm, the acicular ratio is preferably 3 to 20, more preferably 3 to 13, and the crystallite size is preferably 130 to 250 °, more preferably 140 to 200 °. It is.

As the hexagonal ferrite powder, barium ferrite and strontium ferrite in the form of fine flat plate, and a part of their Fe atoms are Ti, C
magnetic powders substituted with atoms such as o, Ni, Zn, V, and the like. The shape of the hexagonal ferrite powder has a plate diameter of preferably 0.02 to 0.09 μm, more preferably 0.02 to 0.07 μm, and a plate ratio of preferably 2 to 7, more preferably Is 2-6.

[0020] The magnetic powder used in the first magnetic paint may contain a rare earth element or a transition metal element, if necessary. In the present invention, the magnetic powder may be subjected to a surface treatment in order to improve the dispersibility and the like of the magnetic powder. The surface treatment is
"Characterization of Powder Surfaces"; Academic
The method can be performed by a method similar to the method described in Press and the like, for example, a method of coating the surface of the magnetic powder with an inorganic oxide. At this time, as the inorganic oxide that can be used, Al ₂ O ₃ , Si
O ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , Z
nO and the like. When used, they can be used alone or in combination of two or more. The surface treatment can be performed by an organic treatment such as a silane coupling treatment, a titanium coupling treatment, and an alumina coupling treatment, in addition to the above method.

The binder used in the first magnetic paint contains the vinyl chloride-based resin and / or the cellulose-based resin and, if necessary, other resins and a curing agent.

Examples of the vinyl chloride resin include polyvinyl chloride and copolymers of vinyl chloride with other copolymer monomers. As the other copolymer monomer,
For example, alkanol esters having 2 to 8 carbon atoms of an α-β unsaturated acid such as (meth) acrylic acid-2-hydroxyethyl ester and (meth) acrylic acid-2-hydroxypropyl ester; the following formula: CH ₂ = CR-COO- (C _n
H _2n O) _m -H wherein m is an integer of 2 to 9,
Represents an integer of 2 to 4, and R represents a hydrogen atom or a methyl group.] Esters of polyalkylene glycol and (meth) acrylic acid; 2-hydroxyethyl-2 ′-(meth) Acryloyloxyphthalate, 2-
Mono (meth) acrylates of dihydroxyesters of dicarboxylic acids such as hydroxyethyl-2 ′-(meth) acryloyloxysuccinate; (meth) acrylamides such as N-methylol (meth) acrylamide; di-2 maleate Alkylene glycol esters of unsaturated acid dicarboxylic acids such as hydroxyethyl ester, maleic acid di-4-hydroxybutyl ester, itaconic acid di-2-hydroxypropyl ester; 3-buten-1-ol, 5-hexene-1 Olefin alcohols such as -ol, vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; (meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) ally 3-hydroxypropyl ether, (meth) allyl-2-hydroxybutyl ether, (meth) allyl-3-hydroxybutyl ether,
Mono (meth) allyl ethers of alkylene glycols such as (meth) allyl-4-hydroxybutyl ether and (meth) allyl-6-hydroxyhexyl ether; diethylene glycol mono (meth) allyl ether, dipropylene glycol mono (meth) allyl ether, etc. Polyoxyalkylene glycol (meth) monoallyl ether; glycerin mono (meth) allyl ether, (meth)
Halogen-substituted (poly) alkylene glycol such as allyl-2-chloro-3-hydroxypropyl ether and (meth) allyl-2-hydroxy-3-chloropropyl ether, mono- (meth) allyl ether of hydroxy-substituted product, eugenol (Meth) allyl ethers of polyhydric phenols such as isoeugenol and its halogen-substituted products; (meth) alkylene glycols such as (meth) allyl-2-hydroxyethylthioether and (meth) allyl-2-hydroxypropylthioether Mono (meth) of polyhydroxy compounds such as allyl thioether
Allyl ethers, mono (meth) thioallyl ethers;
Vinyl alcohol; (meth) allyl alcohol and the like.

Of these, mono (meth) allyl ethers and mono (meth) thioallyl ethers of polyhydroxy compounds are preferred from the viewpoint of thermal stability and reactivity.

In obtaining the copolymer of vinyl chloride and another copolymer monomer, the ratio of the amount of vinyl chloride to other copolymer monomer (former / latter; weight ratio) is 40.
/ 60 to 99/1, particularly preferably 50/50 to 95/5.

In the present invention, the above-mentioned polyvinyl chloride and the copolymer of the above-mentioned vinyl chloride and other copolymer monomers used as the above-mentioned vinyl chloride resin include -COOM, -SO ₃ M,- OSO ₃ M, -P = O
(OM ') ₂ , -OP = O (OM') ₂ [where M
Represents a hydrogen atom, an alkali metal or an ammonium group, and M ′ represents a hydrogen atom, an alkali metal, an ammonium group or an alkyl group having 1 to 20 carbon atoms.], -OH,-
^{_{NR 2, -N + R 3 (}} R is a hydrocarbon group having 1 to 20 carbon atoms), an epoxy group, -SH, -CN, 1 or more polar groups selected from the group consisting of sulfo betaine To
Those introduced by copolymerization or addition reaction are preferably used. At this time, the content of the polar group is preferably 10 ^-1 to 10 ^-6 eq / g, and more preferably ¹ to 10 ^-6 eq / g.
0 ^-2 to 10 ^-6 eq / g.

Specific examples of the vinyl chloride resin include “MR110”, “MR115”, and “MR11”.
3 "," MR112 "," MR105 "," MR10 "
4 "(trade name, manufactured by Nippon Zeon Co., Ltd.)," VAG
H "," VYHH "," VMCH "," VAGF ",
"VAGD", "VROH", "VYNC", "VMC"
C "," PKHJ "," PKHC "," PKFE ",
Commercially available products such as "XYHL", "XYSG", and "PKHH" (both trade names, manufactured by Union Carbide Co., Ltd.) can be used. The vinyl chloride resin has a number average molecular weight of 2,000 to 30,000, particularly 3,000 to 2,000.
5,000 are preferably used.

Examples of the above-mentioned cellulose resin include nitrocellulose, cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, ethyl cellulose, methyl ethyl cellulose, carboxymethyl cellulose, acetyl cellulose and the like. , "BTH-1
/ 2 "," BTH- ／ "," BTH- ／ ",
"BTH-1 / 16", "BT-SL", "VX-1"
Commercial products such as those described above (trade names, manufactured by Asahi Kasei Corporation) can be used. The cellulosic resin has a number average molecular weight of 2,000 to 35,000, especially 3,000.
Those having 0 to 33,000 are preferably used.

Examples of the other resins include thermoplastic resins such as polyester, polyurethane, and epoxy resins, thermosetting resins, and reactive resins in addition to the above-mentioned vinyl chloride resins and / or cellulose resins. Also, JP-A-57-162128, page 2, upper right column, line 19-
Resins and the like described on page 19, lower right column, line 19, and the like are included. Examples of the curing agent include polyisocyanate compounds. Specific examples of the polyisocyanate compound include diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, and trimethylolpropane of these diisocyanates. Examples include an adduct, a burette-bonded type, an isocyanurate type, and the like, and a commercially available product can also be used.

The above-mentioned vinyl chloride-based resin and / or cellulose-based resin, the above-mentioned other resins and the above-mentioned curing agent used as required, can be used alone or as a mixture when used.

In the case where the above-mentioned vinyl chloride-based resin and the above-mentioned cellulose-based resin are mixed and used in the first magnetic layer, the content ratio of the vinyl chloride-based resin and the cellulose-based resin (the former / the latter) ) Is preferably 2/9 by weight
It is 8 to 98/2, more preferably 30/70 to 95/5.

The amount of the vinyl chloride resin and / or cellulose resin used in the first magnetic paint is preferably 10 to 90% by weight, more preferably 15 to 80% by weight, based on the whole binder. It is. The amount of the curing agent used is preferably 5 to 60% by weight, more preferably 10 to 60% by weight, based on the entire binder.
50% by weight.

Further, the binder in the first magnetic paint preferably contains a resin having a polar group for improving dispersibility and the like. The amount of the binder used in the first magnetic paint is 3 to 100 parts by weight of the magnetic powder.
The amount is preferably 50 parts by weight, particularly preferably 5 to 40 parts by weight.

As the solvent in the first magnetic paint, ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, etc. And, specifically, JP-A-57-16
No. 2128, page 3, lower right column, line 17 to page 4, lower left column 1,
The solvents described in line 0 and the like can be used. The solvent is preferably used in an amount of 80 to 500 parts by weight, preferably 100 to 35 parts by weight, per 100 parts by weight of the magnetic powder.
0 parts by weight is more preferred.

The above-mentioned first magnetic paint contains additives commonly used in magnetic recording media such as dispersants, lubricants, abrasives, antistatic agents, rust preventives, and fungicides. Can be added as needed. As the above additives,
Specifically, it is described in page 2, upper left column, line 6 to page 2, upper right column, line 10 and page 3, upper left column, line 6 to page 3, upper right column, line 18 of JP-A-57-162128. And various additives.

In order to prepare the first magnetic paint, for example, a binder containing the above magnetic powder and the above vinyl chloride resin and / or cellulose resin is put into a Nauta mixer or the like together with a part of the solvent. And pre-mixed to obtain a mixture,
The obtained mixture is kneaded by a continuous pressure kneader or the like,
Next, after dilution with a part of the solvent and dispersion treatment using a sand mill or the like, an additive such as a lubricant is mixed, and filtered,
Further, a method of mixing the remaining solvent can be used.

The thickness of the first magnetic layer is 0.05 to
1.0 μm, preferably 0.05 to 0.8 μm
Is more preferable. If less than 0.05 μm,
Uniform coating becomes difficult, and durability may decrease,
If it exceeds 1.0 μm, the thickness loss increases, and the overwrite characteristics may be significantly reduced.

[0037] The second magnetic layer in the magnetic recording medium is disposed adjacent to the first magnetic layer of the present invention, a strong magnetic <br/> powder and vinyl resin and / or cellulose resin chloride And a layer containing a second magnetic paint applied on the support. The second magnetic coating, paint mainly composed of a binder and a solvent containing the ferromagnetic powder and the salt of a vinyl resin and / or cellulose-based resin is preferably used.

[0038]

[0039]

[0040]

[0041]

Examples of the ferromagnetic powder used in the second magnetic paint include a ferromagnetic metal powder mainly composed of iron and a hexagonal ferrite powder. The coercive force of the ferromagnetic metal powder is preferably 1400 to 2500 Oe. The coercive force of the hexagonal ferrite powder is preferably 900 to 2300 Oe.
More preferably, it is 0 to 2000 Oe. When the coercive force of the ferromagnetic metal powder and the hexagonal ferrite are respectively less than the above lower limits, the short-wavelength RF output is reduced because of easy demagnetization. Is insufficient, the writing ability is insufficient, and the overwrite characteristics are further deteriorated.

The saturation magnetization of the ferromagnetic metal powder is
It is preferably from 100 to 180 emu / g,
More preferably, it is 50 emu / g. The saturation magnetization of the hexagonal ferrite powder is preferably 30 to 70 emu / g, and more preferably 45 to 70 emu / g. When the saturation magnetization of the ferromagnetic metal powder and the hexagonal ferrite powder are each less than the lower limit, the filling rate of the magnetic powder is reduced, the output is reduced, and when the upper limit is exceeded. Therefore, it is necessary to reduce the binder, the interaction between the magnetic powders increases, and as a result, the magnetic powders are in an agglomerated state, and it is difficult to obtain a desired output. Is preferred.

Therefore, the coercive force of the second magnetic layer containing the ferromagnetic metal powder is preferably 500 to 24.
00 Oe, more preferably 1250 to 2000 Oe, and the coercive force of the second magnetic layer containing the hexagonal ferrite powder is preferably 500 to 2200 Oe, more preferably 1250 to 2000 Oe. When the ferromagnetic metal powder is contained, the second magnetic layer preferably has a saturation magnetic flux density of 100 to 4500 gauss, more preferably 200 to 3000 gauss. The saturation magnetic flux density of one magnetic layer is preferably 100 to 2500 Gauss, more preferably 200 to 2000 Gauss.

The ferromagnetic metal powder has a metal content of 5
0% by weight or more, and 60% by weight or more of the metal component is Fe.
Ferromagnetic metal powder. Specific examples of the ferromagnetic metal powder include, for example, Fe-Co, Fe-Ni,
Fe-Al, Fe-Ni-Al, Fe-Co-Ni, F
e-Ni-Al-Zn, Fe-Al-Si, and the like. The shape of the ferromagnetic metal powder is needle-like or spindle-like, and its major axis is preferably 0.05 to 0.25 μm,
More preferably, it is 0.05 to 0.2 μm, and the acicular ratio is preferably 3 to 20, more preferably 3 to 13. Further, the crystallite size is preferably 130 to 250.
Å, more preferably 140 to 200Å.

As the hexagonal ferrite powder, barium ferrite and strontium ferrite in the form of fine flat plates, and a part of their Fe atoms are Ti, C
magnetic powders substituted with atoms such as o, Ni, Zn, V, and the like. The shape of the hexagonal ferrite powder is plate-like, and the plate diameter is preferably 0.02 to 0.09.
μm, more preferably 0.02 to 0.07 μm, and the tabular ratio is preferably 2 to 7, more preferably 2 to 6.
It is.

As the ferromagnetic powder, the above-mentioned hexagonal ferrite powder, in particular, a hexagonal ferrite powder having a plate-like shape is preferably used.

The binder used in the second magnetic paint contains the vinyl chloride resin and / or the cellulose resin, and further contains other resins and curing agents as required. Examples of the vinyl chloride resin include the vinyl chloride resin used in the first magnetic paint described above. Further, as the above-mentioned cellulose-based resin, the above-mentioned cellulose-based resin used for the first magnetic coating material and the like can be mentioned. The other resin and the curing agent include the other resin and the curing agent used in the first magnetic paint.

In the case where the above-mentioned vinyl chloride resin and the above-mentioned cellulose resin are mixed and used in the above-mentioned second magnetic layer, the content ratio of the above-mentioned vinyl chloride resin and the above-mentioned cellulose resin (the former / the latter) ) Is preferably 2/9 by weight
It is 8 to 98/2, more preferably 30/70 to 95/5. Further, the same ferromagnetic powder as that used for the first magnetic paint can also be used.

The amount of the vinyl chloride resin and / or the cellulose resin used in the second magnetic paint is preferably 10 to 90% by weight, more preferably 15 to 80% by weight, based on the whole binder. is there. The amount of the curing agent is preferably 5 to 5% with respect to the entire binder.
It is 60% by weight, more preferably 10 to 50% by weight.

Further, it is preferable that the binder used in the second magnetic paint contains a resin having a polar group for improving dispersibility and the like. The amount of the binder used in the second magnetic paint is 20 to 12 with respect to 100 parts by weight of the magnetic powder used in the second magnetic paint.
The amount is preferably 0 parts by weight, particularly preferably 30 to 110 parts by weight.

As the solvent used for the second magnetic paint, the same solvent as the solvent used for the first magnetic paint can be used. In addition, the second
The mixing ratio of the solvent in the magnetic paint of the second
The amount is preferably 80 to 500 parts by weight, more preferably 100 to 350 parts by weight, based on 100 parts by weight of the magnetic powder used for the magnetic paint.

In addition, a dispersant,
Lubricants, abrasives, antistatic agents, rust inhibitors, fungicides, and additives that are commonly used in magnetic recording media such as curing agents,
It can be added as needed. Specific examples of the above-mentioned additive include JP-A-57-162128, page 2, upper left column, line 6 to page 2, upper right column, line 10 and page 3, upper left column, line 6 to page 3, upper right column 18 Various additives described in the column and the like can be mentioned.

Further, a non-magnetic powder can be added to the second magnetic paint. The non-magnetic powder is not particularly limited as long as it is non-magnetic, but carbon black, graphite, titanium oxide, barium sulfate, zinc sulfide, magnesium carbonate, calcium carbonate, zinc oxide,
Calcium oxide, magnesium oxide, tungsten disulfide, molybdenum disulfide, boron nitride, tin dioxide, silicon dioxide, nonmagnetic chromium oxide, alumina, silicon carbide, cerium oxide, corundum, artificial diamond, nonmagnetic iron oxide, garnet , Garnet, silica, silicon nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, diatomaceous earth, dolomite, resinous powders, among others, carbon black, titanium oxide, barium sulfate, calcium carbonate, alumina And non-magnetic iron oxide are preferably used. In order to improve the dispersibility of the nonmagnetic powder, the nonmagnetic powder is subjected to the same surface treatment as the surface treatment performed on the magnetic powder used in the first magnetic paint. You may.

Further, the thickness of the second magnetic layer is set to 0.1.
It is preferably from 2 to 5 μm, more preferably from 0.5 to 4 μm, and most preferably from 0.5 to 2.5 μm. If it is less than 0.2 μm, the resulting magnetic recording medium will have a low stiffness, and if it exceeds 5 μm, the overwrite characteristics will be reduced.

Thus, in the magnetic recording medium of the present invention, the content of the binder in the first magnetic layer and the content of the binder in the second magnetic layer have the following formula, preferably: The content of the vinyl chloride resin or the cellulose resin in the first magnetic layer and the content of the vinyl chloride resin or the cellulosic resin in the second magnetic layer preferably have the following relationship. 0.6 ≦ (AB) / B ≦ 6 ′ 0.8 ≦ (AB) / B ≦ 5 0.4 ≦ (CD) / D ≦ 11 ′ 0.6 ≦ (CD) / D ≦ 10 wherein A is the content of the binder in the second magnetic layer /
Second content of ferromagnetic powder in the magnetic layer indicates a>, B is
<Content of binder in first magnetic layer / content of magnetic powder in first magnetic layer> indicates C, ((vinyl chloride resin and / or cellulose resin in second magnetic layer) shows the content) / second content of ferromagnetic powder in the magnetic layer of the resin>, D is <(content of the first polyvinyl chloride resin in the magnetic layer and / or cellulose resin) / Content of Magnetic Powder in First Magnetic Layer>. ]

If the value of the above expression is less than 0.6, the running durability of the magnetic recording medium is degraded, and errors such as the head clog phenomenon are liable to occur. It is difficult to form the magnetic powder or the like easily, and errors such as dropping of the magnetic powder and the like are likely to occur. If the value of the above expression is less than 0.4, the running durability of the magnetic recording medium is deteriorated, and errors such as a head clog phenomenon are likely to occur. If the value exceeds 11, the interface between the layers is good. Errors or errors such as dropping of magnetic powder or the like are likely to occur.

The magnetic recording medium of the present invention is for audio,
It is suitable as a magnetic tape for video or computer use, but can also be applied to other magnetic recording media such as floppy disks.

Next, an outline of a method for manufacturing the magnetic recording medium of the present invention will be described. First, the first magnetic paint and the second magnetic paint are wet-coated on the support such that the dry film thicknesses of the first magnetic layer and the second magnetic layer are respectively the above-mentioned thicknesses. Simultaneous multi-layer coating is performed by an on-wet method to form coating films of the first and second magnetic layers. That is, the first magnetic layer is preferably applied and formed when the second magnetic layer is wet. Next, after performing a magnetic field orientation treatment on the coating film, a drying treatment is performed and the film is wound. Thereafter, a calender treatment is performed if necessary, and then a back coat layer is further formed as necessary. Next, if necessary, for example, when obtaining a magnetic tape, the magnetic tape is subjected to aging treatment at 40 to 70 ° C. for 6 to 72 hours, and slit into a desired width.

The above simultaneous multi-layer coating method is disclosed in
No. 883, column 42, line 31 to column 43, line 31, etc., and the first magnetic layer is dried before the second magnetic paint forming the second magnetic layer is dried. A method of applying the first magnetic paint to be formed, wherein a boundary surface between the first magnetic layer and the second magnetic layer is smoothed and a surface of the first magnetic layer is formed. As a result, a magnetic recording medium with little dropout, capable of coping with high-density recording, and having excellent durability of the coating film (the first magnetic layer and the second magnetic layer) can be obtained.

The magnetic field orientation treatment is performed before the first and second magnetic paints are dried. For example, when the magnetic recording medium of the present invention is a magnetic tape, the first magnetic paint is treated. About 500 Oe or more in the direction parallel to the coating surface of
Preferably, a method of applying a magnetic field of about 1,000 to 10,000 Oe, a method of passing the first and second magnetic paints through a solenoid of 1000 to 10,000 Oe in a wet state, and the like can be used.

The drying treatment is performed, for example, at 30 to 120 ° C.
In this case, the degree of drying of the coating film can be controlled by controlling the temperature of the gas and the supply amount of the gas.

The calendering treatment can be performed by a super calendering method in which a metal roll and a cotton roll or a synthetic resin roll, a metal roll and a metal roll are passed between two rolls. Also,
The conditions of the calendering treatment are as follows.
５００500 kg / cm.

The back coat layer provided as necessary is provided on the back surface of the support (the surface on which the first and second magnetic layers are not provided).
It is obtained by applying a back coat paint, which is usually used for forming a back coat layer, on the support.

In the production of the magnetic recording medium of the present invention, a finishing step such as a polishing or cleaning step for the surface of the magnetic layer can be performed if necessary. The application of the first and second magnetic paints can also be performed by a generally known sequential coating method.

[0066]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. Example 4 below is an example of the present invention,
Examples 1 to 3 below are reference examples.

Example 1 First magnetic paint A having the following composition
And a second magnetic paint (a) having the following composition in a combination shown in [Table 1], and using a backcoat paint having the following composition as the backcoat paint, according to the following [Method for producing magnetic recording medium]. Then, a magnetic tape as a magnetic recording medium in which the first and second magnetic layers were formed by the first and second magnetic paints shown in [Table 1] was obtained. The coercive force and the saturation magnetic flux density of the first magnetic layer formed using the first magnetic paint A were measured according to the [measurement method] described later.
The coercive force of the first magnetic layer formed by using
e, and the saturation magnetic flux density was 3600 gauss.

First magnetic paint A: 100 parts by weight of acicular metal magnetic powder mainly composed of iron (coercive force: 1860 Oe, saturation magnetization: 137 emu / g, average major axis length: 0.1 μm) Alumina (average particle size: 0.1 μm) 9 parts by weight ・ Carbon black (average primary particle size 50 nm) 1 part by weight ・ MR104 10 parts by weight [trade name, manufactured by Zeon Corporation, sulfonic acid group-containing vinyl chloride resin (GPC number average molecular weight 17) 7,000)]-Sulfonic acid group-containing polyurethane 7 parts by weight (GPC number average molecular weight 23,000)-Stearic acid 2 parts by weight-2-ethylhexyl oleate 1.5 parts by weight-"Coronate HX" 4.5 parts by weight [product Name, Nippon Polyurethane Industry Co., Ltd., polyisocyanate compound] 100 parts by weight of methyl ethyl ketone 60 parts by weight of toluene Non 100 parts by weight

Second magnetic paint (a)・ 70 parts by weight of acicular α-iron oxide (average major axis length 0.07 μm) ・ 32 parts by weight of Mn-Zn ferrite (oxide soft magnetic powder) (average particle diameter) 0.04 μm) Carbon black (average primary particle size 0.023 μm) 3.5 parts by weight Alumina (average particle size 0.2 μm) 3 parts by weight “MR104” 12 parts by weight [trade name, Zeon Corporation] Sulfonate group-containing vinyl chloride resin (GPC number average molecular weight 17,000)]-Sulfonate metal group-containing polyurethane 6 parts by weight (GPC number average molecular weight 23,000)-"Coronate L" 3.5 parts by weight [ (Trade name, manufactured by Nippon Polyurethane Industry Co., Ltd., polyisocyanate) 2 parts by weight of oleyl oleate 1 part by weight of myristic acid 60 parts by weight of methyl ethyl ketone 30 parts by weight of toluene・ 90 parts by weight of cyclohexanone

(Blending of backcoat paint) 32 parts by weight of carbon black (average primary particle size 0.028 μm) 8 parts by weight of carbon black (average primary particle size 0.052 μm) 20 parts by weight of “Nipporan 2301” Name, polyurethane manufactured by Nippon Polyurethane Industry Co., Ltd.] 20 parts by weight of nitrocellulose (viscosity display 1/2 second manufactured by Hercules Powder Co.) 4 parts by weight of "D-250N" [trade name, Takeda Pharmaceutical Co., Ltd.] Polyisocyanate manufactured by Co., Ltd.] 5 parts by weight of copper phthalocyanine 1 part by weight of stearic acid 120 parts by weight of methyl ethyl ketone 120 parts by weight of toluene 120 parts by weight of cyclohexanone

[Production of Magnetic Recording Medium] The first magnetic paint and the second magnetic paint were dried on the surface of a polyethylene naphthalate film having a thickness of 6 μm to a thickness of 0.3 μm and 2.5 μm, respectively. So that
Simultaneous multi-layer coating was performed by an on-wet method to form coating films of a first magnetic layer and a second magnetic layer. Next, the coating film was passed through a 5000 Oe solenoid in a wet state to perform a magnetic field orientation treatment, dried at 60 to 100 ° C., and wound up. Then, at 85 ° C, 300
After performing a calendering process under the condition of kg / cm to form the first and second magnetic layers, a backcoat paint is applied on the back surface of the support so that the dry thickness becomes 0.5 μm,
After performing a drying treatment at 90 ° C., it was wound up. afterwards,
Aging treatment at 50 ° C. for 16 hours, 3.81 m
By slitting to a width of m, a magnetic tape having a width of 3.81 mm (value of the above equation = 2.13, value of the above equation = 2.75) was obtained. The resulting magnetic tape was evaluated for surface roughness, output (4.7 MHz), overwrite characteristics, and running durability as described below. The results are shown in [Table 1].

[Measurement Method] ◎ Coercive Force and Saturation Magnetic Flux Density The above-mentioned support and the second magnetic layer coated on the above-mentioned support and the second magnetic layer were adhered to the support and the second magnetic layer using an adhesive tape.
Only the first magnetic layer is peeled off from the magnetic layer, and the first magnetic layer is punched into a predetermined size and shape, and the coercive force and the saturation magnetic flux density are measured using a vibrating magnetometer at an applied magnetic field of 10 kOe. Each was measured. ◎ Surface roughness of magnetic recording medium Surface roughness Ra The obtained magnetic recording medium was manufactured by Tokyo Seimitsu Co., Ltd.
The measurement was performed using a surface roughness shape measuring instrument (trade name: Surfcom 553A) under the conditions of a needle radius of 2 μm, a load of 30 mg, a magnification of 200,000, and a cutoff of 0.08 mm.
Note that Ra (center line average roughness) is obtained by extracting a portion of the measurement length L from the roughness curve in the direction of the center line, setting the center line of the extracted portion as the X axis and the direction of the vertical magnification as the Y axis. When the length curve is represented by y = f (x), the value obtained by the following equation is represented by [nm].

[0073]

(Equation 1)

Output (4.7 MHz) The obtained 3.81 mm wide magnetic tape was loaded into a DAT cassette to obtain a test DAT tape cassette. The obtained test DAT tape cassette was inserted into MediaLogi.
c, trade name "Tape Evaluator Mod
el 4500 "and 4.7
A signal of MHz was recorded, and the output (reproduced output) when the signal was reproduced was measured. Note that the recording wavelength of 4.7 MHz is 0.1.
It was 67 μm. Note that the output value of the first embodiment is set as a reference (0
dB). ◎ Overwrite characteristics DDS-1 drive (DAT drive for data recording)
, A 1.2 MHz or 130 KHz signal was recorded, and then a 4.7 MHz or 1.5 MHz signal was overwritten, and the output level of the remaining 1.2 MHz or 130 KHz signal was measured. Note that Comparative Example 2 was used as a reference.
Also, the lower the residual output level, the better the overwrite characteristics. ◎ Running durability First, the initial block error rate (1st-BER) of the obtained magnetic tape was measured using a DDS-1 drive (BO
T: Beginning Of Tape and EOT: End Of Tape, respectively. Then, the 10th block error rate (10th-BER) was measured (average value of the entire length), and the obtained measurement value was compared with the initial block error rate. In addition, the one with little rise (10th-BER / 1st-BER)
Indicates good running durability.

Example 2 Using the following first magnetic paint B and the following second magnetic paint (b), a magnetic tape (value of the above equation = 1.25, The value of the equation = 1.06) was obtained, and the obtained magnetic tape was evaluated in the same manner as in Example 1. When the coercive force and the saturation magnetic flux density of the first magnetic layer formed using the first magnetic paint B were measured in the same manner as in Example 1, the first magnetic layer formed using the first magnetic paint B was measured. The coercive force of the magnetic layer is 1900 Oe
And the saturation magnetic flux density was 3585 gauss. First Magnetic Coating B The amount of the “MR104” was changed from 10 parts by weight to 12.5 parts by weight, and the amount of the sulfonic acid group-containing polyurethane was changed to 7 parts.
The same as the above-mentioned first magnetic coating material A except that the amount of “Coronate HX” was changed from 4.5 parts by weight to 5 parts by weight instead of 6 parts by weight. Second magnetic paint (b) The amount of Mn-Zn ferrite was changed from 32 parts by weight to 35 parts by weight, and the amount of "MR104" was changed from 12 parts by weight to 9 parts by weight. Same as the above second magnetic paint (a) except that the blending amount was changed from 6 parts by weight to 6.5 parts by weight, and the blending amount of “Coronate L” was changed from 3.5 parts by weight to 3 parts by weight .

Example 3 Using the following first magnetic paint W and the following second magnetic paint (e), a magnetic tape (the value of the above formula = 1.30, The value of the equation = 2.03) was obtained, and the obtained magnetic tape was evaluated in the same manner as in Example 1. When the coercive force and the saturation magnetic flux density of the first magnetic layer formed using the first magnetic paint W were measured in the same manner as in Example 1, the first magnetic layer formed using the first magnetic paint W was measured. The coercive force of the magnetic layer is 1895 Oe
And the saturation magnetic flux density was 3605 Gauss. The amount of the first magnetic paint W “MR104” was changed from 10 parts by weight to 8.5 parts by weight, the amount of the sulfonic acid group-containing polyurethane was changed from 7 parts by weight to 6 parts by weight, and “VX-1” was further changed. 3.5 parts by weight of a nitrocellulose resin (trade name, manufactured by Asahi Kasei Kogyo KK) (number average molecular weight 7300) was added, and the blending amount of "Coronate HX" was changed from 4.5 parts by weight to 5 parts by weight. Other than the above, it is the same as the first magnetic paint A described above. Second magnetic paint (e) The above second magnetic paint (b) except that sulfobetaine-containing polyurethane “E-780” (manufactured by Takeda Pharmaceutical Co., Ltd.) was used instead of the sulfonic acid metal base-containing polyurethane.
Same as.

Example 4 The procedure of Example 1 was repeated except that the first magnetic coating material A and the second magnetic coating material (f) having the following composition were used. = 3.4
8, the value of the above formula = 5.16) was obtained, and the obtained magnetic tape was evaluated in the same manner as in Example 1. Magnetic paint (f)・ 33 parts by weight of hexagonal ferrite powder (hexagonal barium ferrite, coercive force: 1690 Oe, saturation magnetization: 57 emu / g, average plate diameter: 0.05 μm, plate ratio: 4) ・ needle shape Α-Fe ₂ O ₃ 67 parts by weight (major axis length: 0.15 μm, axial ratio: 8, specific surface area: 52 m ² / g) 6.5 parts by weight of alumina (average particle diameter 0.3 μm) 6.5 carbon parts (Average primary particle diameter: 20 μm) 2.5 parts by weight ・ PVC copolymer 12.2 parts by weight (“MR-110”, trade name, manufactured by Nippon Zeon Co., Ltd.) ・ Polyurethane resin 4.5 parts by weight (“UR- "8300", trade name, manufactured by Toyobo Co., Ltd.) 4 parts by weight of "Coronate HX" [trade name, polyisocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd.] 2 parts by weight of butyl stearate 2 parts by weight of myristic acid・ Methyle Ketone 84 parts Toluene 56 parts Cyclohexanone 28 parts by weight

Comparative Example 1 Using the following first magnetic paint C and the above second magnetic paint (a), a magnetic tape (the value of the above formula = 0.36, The value of the equation = 0.29) was obtained, and the obtained magnetic tape was evaluated in the same manner as in Example 1. When the coercive force and the saturation magnetic flux density of the first magnetic layer formed using the first magnetic paint C were measured in the same manner as in Example 1, the first magnetic layer formed using the first magnetic paint C was measured. The coercive force of the magnetic layer is 1896 Oe
And the saturation magnetic flux density was 3583 gauss. The amount of the first magnetic paint C "MR104" was changed from 10 parts by weight to 29 parts by weight, the amount of the sulfonic acid group-containing polyurethane was changed from 7 parts by weight to 12 parts by weight, and the amount of the "Coronate HX" was changed. Same as the above-mentioned first magnetic coating material A except that the amount was changed from 4.5 parts by weight to 8.5 parts by weight.

Comparative Example 2 Using the following first magnetic paint D and the following second magnetic paint (c), a magnetic tape (the value of the above formula = 7.41; The value of the equation = 12.17) was obtained.
The same evaluation as in Example 1 was performed. The results are shown in [Table 1]. When the coercive force and the saturation magnetic flux density of the first magnetic layer formed using the first magnetic paint D were measured in the same manner as in Example 1, the first magnetic layer formed using the first magnetic paint D was measured. The coercive force of the magnetic layer was 1890 Oe, and the saturation magnetic flux density was 3607 gauss. The amount of the first magnetic paint D “MR104” was changed from 10 parts by weight to 9 parts by weight, the amount of the sulfonic acid group-containing polyurethane was changed from 7 parts by weight to 6 parts by weight, and the amount of the “Coronate HX” was changed. Same as the above-mentioned first magnetic coating material A except that the amount was changed from 4.5 parts by weight to 3.5 parts by weight. Second magnetic paint (C) The amount of Mn-Zn ferrite was changed from 32 parts by weight to 27 parts by weight, the amount of "MR104" was changed from 12 parts by weight to 32 parts by weight, and the amount of "Coronate L" was changed. To 3.5
Same as the second magnetic paint (a) except that the weight part was changed to 4 parts by weight.

Comparative Example 3 Using the following first magnetic paint E and the following second magnetic paint (d), a magnetic tape (the value of the above equation = 6.91; The value of the equation = 9.71) was obtained, and the obtained magnetic tape was evaluated in the same manner as in Example 1. The results are shown in [Table 1]. When the coercive force and the saturation magnetic flux density of the first magnetic layer formed using the first magnetic paint E were measured in the same manner as in Example 1, the first magnetic layer formed using the first magnetic paint E was measured. The coercive force of the magnetic layer was 1868 Oe, and the saturation magnetic flux density was 3578 Gauss. The amount of the first magnetic paint E “MR104” was changed from 10 parts by weight to 6 parts by weight, the amount of the sulfonic acid group-containing polyurethane was changed from 7 parts by weight to 4 parts by weight, and the amount of the “Coronate HX” was changed. Except having changed from 4.5 parts by weight to 4 parts by weight,
The same as the magnetic paint A. Second magnetic paint (d) The amount of Mn-Zn ferrite was changed from 32 parts by weight to 28 parts by weight, and the amount of "MR104" was changed from 12 parts by weight to 18 parts by weight. Same as the above second magnetic paint (a) except that the blending amount was changed from 6 parts by weight to 9 parts by weight, and the blending amount of “Coronate L” was changed from 3.5 parts by weight to 4 parts by weight.

[0081]

[Table 1]

As is clear from the results shown in [Table 1],
The uppermost layer (first magnetic layer ) of the magnetic recording medium of the present invention
Layer but which contains a binder comprising a magnetic powder and a vinyl resin and / or cellulose resin chloride, adjacent thereto
(The second magnetic layer) is composed of a ferromagnetic powder, a vinyl chloride resin and
And / or a binder containing a cellulosic resin, wherein the content of the binder in the first magnetic layer and the content of the binder in the second magnetic layer have a specific relationship, In addition, the content of the vinyl chloride resin and / or the cellulose resin in the first magnetic layer and the content of the vinyl chloride resin and / or the cellulose resin in the second magnetic layer have a specific relationship. Have
It turns out that it is excellent in output characteristics, overwrite characteristics, running durability and surface smoothness.

[0083]

The magnetic recording medium of the present invention has good surface smoothness and excellent output characteristics, overwrite characteristics and running durability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a magnetic recording medium according to the present invention.

────────────────────────────────────────────────── (5) References JP-A-7-29153 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/62-5/718 B32B 33 / 00

Claims (2)

(57) [Claims] 1. A semiconductor device comprising: a support; and a plurality of magnetic layers provided on the support, wherein the plurality of magnetic layers include a first magnetic layer provided as an uppermost layer; in the magnetic recording medium and a second magnetic layer provided adjacent to the magnetic layer, the first magnetic layer described above, and a binder containing a magnetic powder and a vinyl resin and / or cellulose resin chloride contain,
The second magnetic layer is made of a ferromagnetic powder and a vinyl chloride resin.
And / or a binder containing a cellulose-based resin, wherein the content of the binder in the first magnetic layer and the content of the second
And the content of the binder in the magnetic layer of the first magnetic layer has the relationship of the following formula, and the vinyl chloride resin and / or
Alternatively, a magnetic recording medium characterized in that the content of the cellulose resin and the content of the vinyl chloride resin and / or the cellulose resin in the second magnetic layer have the following relationship. 0.6 ≦ (AB) / B ≦ 6 0.4 ≦ (CD) / D ≦ 11 [where A is the content of the binder in the second magnetic layer /
Second content of ferromagnetic powder in the magnetic layer indicates a>, B is
<Content of binder in first magnetic layer / content of magnetic powder in first magnetic layer> indicates C, ((vinyl chloride resin and / or cellulose resin in second magnetic layer) shows the content) / second content of ferromagnetic powder in the magnetic layer of the resin>, D is <(content of the first polyvinyl chloride resin in the magnetic layer and / or cellulose resin) / Content of Magnetic Powder in First Magnetic Layer>. ] 2. The method according to claim 1, wherein the ferromagnetic powder is a plate-like hexagonal ferrite.
2. The magnet according to claim 1, wherein the magnetic powder is light powder.
Recording medium .